Examples of oily components used in cosmetics include hydrocarbons, higher alcohols, ester oils, animal and plant oils, silicone oils, polyhydric alcohols, polyhydric alcohol ethers and alkyl glyceryl ethers. Because they have such effects as making the skin softer and smoother, protecting and moisturizing the skin, and removing excess oils from the skin, these components are used as starting materials in various products including basic skincare products such as cleansing oils, creams and beauty essences; make-up such as foundations, sunscreens, mascara, eye shadow and rouge; hair products such as shampoos, rinses, conditioners, hair dyes and styling products; and lip cosmetics such as lipstick and lip gloss.
With ordinary oily components, there are often concerns about the sticky feeling characteristic of oily components, safety and irritation to the skin, and stability when compounded in cosmetics and the like. Of these oily components, ester oils and silicone oils have relatively little sticky feeling and are known to be highly stable and non-irritating, so they are often preferred as oily components for compounding in cosmetics. However, the problem is that these are not very stable when compounded in cosmetics. There is commercial demand for techniques to further improve the stability of cosmetics containing ester oils and silicone oils, and, for example, additives have been developed for emulsifying ester oils and silicone oils used in cosmetics containing water, and for thickening or gelling ester oils and silicone oils used in cosmetics containing no water. In the latter case, however, there is room for further development.
For example, gelling agents that have been developed include a N-acylamino acid monoamide monoalkyl ester (PTL 1) that can harden and gel a wide variety of oily bases including silicone, conferring a hard, waxy consistency, and a silicone compound (PTL 2) containing a polyoxyalkylene group and an organic group having one or more terminal hydroxyl groups, and capable of gelling silicone oil and conferring a relatively soft, pasty consistency. However, since these gelling agents can only confer a specified waxy or pasty consistency or properties, their range of use is limited for cosmetic applications. Polyurethane compounds (PTL 3, 4) and the like have therefore been developed that confer a gel-like or jelly-like consistency that is applicable to a wide range of cosmetic applications and is more elastic, more pleasant to the touch and easier to spread on the skin, but these additives are added to cosmetics in extremely large quantities, and the thickening and gelling effects are unsatisfactory. Thickening and gelling of silicone and ester oily components is a widely marketable technology because it can lead to cosmetic diversification or in other words the development of various forms of oil-based products, and should be of interest in the cosmetic industry. There is therefore market demand for the development of thickeners and gelling agents with greater oil thickening effects, and the development of additives that can achieve thickening and gelling effects with the smallest possible added amounts.